The consistency doesn't sweat me a whole lot.
He puts in a shift, and has wild on ball talent. The inconsistency - as far as I can tell - is more a byproduct of being an attacking player on a mid (at best) table team. He just doesn't get the ball a lot, plus mid league teams often play through wide areas, and so variance can disrupt his impact (goals/assists).
Plus, I'll take a touch of inconsistency if it comes alongside some swag. I love my boy Martinelli but his game has become boring and less impactful.